There are many components of an aircraft that are positioned by electromechanical or pneumatic-mechanical actuation systems. In these systems, an electric or pneumatic motor drives an actuator in response to signals from an electronic control unit. To assure that these aircraft components are accurately and correctly positioned, the control unit needs to know position of the actuator moving the component. To achieve this, highly accurate position sensors are used on the actuators to sense the position of the actuator and provide to the control unit a corresponding signal. One such sensor commonly used is a linear variable displacement transducer, (LVDT).
Because of compliance or resilience in the actuator and in the mounting of the actuator, the actuator will amplify displacement oscillations when operating at its natural or resonant frequency. These amplified oscillations are picked up by high accuracy position sensors like the LVDT. The LVDT feeds the oscillation through the control system and as a result can drive the control system unstable.
Accordingly, a need exists for a filtering system that isolates these oscillations from the control unit and thus allow the use of high accuracy sensors.